Phase Linear 700 eats sppeakers

[chuckg]

Hey all --
I've got a Phase Linear 700 that loves to eat speakers. When I turn it on, the speakers cones move out about ten feet and then slowly move back in. This is not good for spiders and surrounds not designed for such extensive excursion. It can also deform the hapless voice coil as it re-enters the gap.

Seriously, though, the speakers move out so far it frightens me, and many drivers have gone to the dump becuae of this "turn on transient."

My cure so far is a big fat switch on each output; a sort of manually operated power-up cycle. I know I coudl build something fancier, but I'd rather fix what is wrong with the amp.

Any ideas?

 

[Stocker]

This is a standard "feature" of many amplifiers, and in fact even some amplifier topologies. A switch will work, as will a relay, if there is nothing "wrong" with your amp.

 

[Netlist]

This seems like rather heavy DC slowly reducing. What does the DMM report?

/Hugo

 

[cyclotronguy]

Back in the day they were know as Flame Linear 700's by all the repair guys. Pretty spectacular eruption when the output stages went pfffft. Check the DC offset.

Cyclotronguy

 

[Netlist]

Yes, and sometimes pretty nasty to repair. Checking ALL semiconductors was a must, even the most innocent 1N4148.

To chuckg: You might want to take a look at this informative webspace: http://www.vintagephase.com/

/Hugo